Our objective is to develop a quantitative model of the neurophysiological mechanism underlying the perception of motion. This will be accomplished by analyzing the response of single neurons in the visual cortex of the cat, using microelectrode techniques. We view a motion-selective neuron as basically a sequence and analyzer which receives temporal impulses of specific wave-shaped from the retina. The sequence analyzer is probably made up of three receptive fields arrayed in a row: a disinhibitory field, D, and excitatory field, E, and an inhibitory field, I. When an object moving in the visual field at the appropriate velocity stimulates these three fields in the order, D, E, then I the cell fires. When the object moves in the visual field in the order I, E, the D the cell does not fire. We believe that the precise wave-shape properties of the temporal retinal pulses (whether very transient or more sustained) determines the velocity range in which the cell discriminates motion-directions. More precisely, the temporal wave shapes plus the spatial disposition of the three receptive fields should completely define the response of the cell. Our research strategy is simple. We plan to measure both the spatial and temporal characteristics of motion-selective neurons in the visual cortex and, in addition, their velocity sensitivity. Various experimental manoeuvers will be used to vary these spatial and temporal characteristics (such as dark adaptation, recording from visual cortex neurons which receives area centralis projections and compare it to visual cortex neurons which receive peripheral visual field projections, recording from "transient response" neurons as well as "sustained response" neurons. Recording from a variety of neurons, and recording from a variety of temporal and spatial conditions, will test our fairly simple model of space-time interaction in motion-direction selective neurons. The same mechanisms will be shown to predict real and apparent movement perception.